Having already written extensively about the movie in my review
of Kathy Hepinstall's Absence of Nectar, I'll only add a few more comments
here. The inspiration for this book, and for the character of Harry
Powell, was Harry
Powers, known as the Bluebeard of Quiet Dell, who was hanged on March
18, 1932, at the West Virginia Penitentiary in Moundsville. Powers
was convicted of killing Asta B. Eicher. a widow, along with her three
children, and another widow, Dorothy Lemke. He may also have killed
a traveling salesman. The story would have been sensational at any
time, but to a nation deep in the Depression, it offered welcome diversion.
Grubb, like Powers, was a resident of Clarksburg, and it's easy to imagine
the grip the story must have exerted on the mind of a teen boy.

At any rate, the novel he wrote has surely captivated the rest of us.
Charles
Laughton used it as the source for the only movie he ever directed,
the failure of which was apparently a devastating
personal blow to him. It can be difficult to find the book these
days, but it's well worth the effort. And the film is now acknowledged
as a true cinema classic.